This invention relates to a switching amplifier and more particularly to a switching amplifier with output pulses having fast times and fall times.
In addition to the well known home television receiver, cathode ray tube displays are being used with increasing frequency for presenting visual images of alpha-numeric information.
To develop an image on a cathode ray tube an electron beam is scanned across the face of the tube in a pattern known as a raster scan. One of the key parameters that determines the quality of the image is called resolution, and resolution is dependent on two characteristics of the display. One of these characteristics is the size of the electron beam and the other, which is not so apparent, is the switching speed of the amplifier driving the electron gun generating the beam.
The compromise between picture quality and amplifier speed is well-known. It is more customarily stated in terms of amplifier or video bandwidth as fully discussed by V. K. Zworkykim and G. A. Morton, in their work entitled "Television," 2nd ed. John Wiley, 1954, pages 171-212. For displays of computer-generated text, such as alpha-numerics or graphics, a more convenient parameter is video risetime. For a linear or non-switching amplifier, bandwidth (BW) and risetime (t.sub.R) are related by the well-known equation: EQU BW .times. t.sub.R = 0.35
for a full discussion of this equation reference is made to the work of E. M. Cherry and D. E. Hopper entitled "Amplifying Devices and Low-Pass Amplifier Design," John Wiley, 1968, page 656. In conventional television the bandwidth requirement has been a major limitation due to FCC regulations on frequency spectrum uses. In computer displays the availability and cost of high speed amplifiers has been the limiting factor.